This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Preliminary research suggests cancer recurring may be reduced if letrozole is taken after five years of tamoxifen. The purpose of this study is to find out whether it is better to receive letrozole or no further treatment after stopping tamoxifen. The second purpose is to determine how the treatment affects the quality of life.